TLDR Wool follicles can grow in a lab with the right nutrients and conditions.
The study developed a method to culture isolated wool follicles from 2-year-old Merino sheep wethers, achieving fiber growth rates of 40-80 µm/day in Williams’ E medium with supplements. Insulin and hydrocortisone at specific concentrations stimulated growth, but higher doses were inhibitory. The follicles maintained structure and showed active DNA and keratin synthesis for up to 7 days, enabling the study of direct effects on wool keratin synthesis independent of systemic metabolism.
67 citations
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January 1992 in “Journal of Investigative Dermatology” 
44 citations
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December 1991 in “Annals of the New York Academy of Sciences” EGF and FGF help hair growth by affecting cell differentiation and fiber growth.
385 citations
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November 1990 in “Journal of Cell Science” Human hair follicles can grow in a lab setting.
40 citations
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July 1989 in “Journal of Cell Science” 25 citations
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January 1988 in “Journal of Investigative Dermatology” 87 citations
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October 1987 in “Journal of Investigative Dermatology”
50 citations
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July 2008 in “British Journal of Dermatology” 138 citations
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March 2007 in “Experimental cell research” Only a few hair-specific keratins are linked to inherited hair disorders.
276 citations
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January 2005 in “International review of cytology” 199 citations
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January 2004 in “The International Journal of Developmental Biology” Hair follicle growth and development are controlled by specific genes and molecular signals.
29 citations
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April 2003 in “Experimental dermatology” Human hair follicles grown in vitro maintain normal keratin patterns and structure.
